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Answer:
The answer.
Explanation:
Group 17 consists of Halogens, and group 18 consists of Noble Gases.
Group 17 are very high electronegativities. They have seven valence electrons. They are highly reactive, especially with alkali metals and alkaline earth.
In group 18 their elements are the most stable due to having the maximum number of valence electrons their outer shell can hold. Therefore, they rarely react with other elements since they are already stable.
Nobel gases are placed there because they are extremely unreactive.
Halogen elements are placed there because they have seven valence electrons, they only require one additional electron to form a full octet.
The elements in group 18 are ureactive compared to the elements in group 17.
The elements in group 17 are called the halogens. They are highly reactive nonmetals and hardly occur in free state in nature. They contain seven valence electrons in their outermost shell and are highly electronegative.
The elements in group 18 are unreactive because they have an already filled outermost shell. They are very different from the halogens even though they occur side by side. They occur side by side because they have eight valence electrons and the halogens have seven valence electrons. Recall that elements in the same group have the same number of valence electrons.
They are not Chemically similar at all in any wise. The elements in group 17 and 18 are mostly gases held together by dispersion forces.
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